Low profile electrical interconnect with fusion bonded contact retention and solder wick reduction

ABSTRACT

An electrical interconnect and a method of making the same. A plurality of contact members are located in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate. A flowable polymeric material located on the second surface of the substrate is fusion bonded to the proximal portions of the contact members so the flowable polymeric material substantially seals the through holes in the substrate. An insulator housing is bonded to the first surface of the substrate with the distal portions of the contact members located in through holes in an insulator housing, so the distal portions are accessible from a second surface of the insulator housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/134,810, filed Mar. 18, 2015 and U.S. Provisional Application No.62/146,550, filed Apr. 13, 2015, the disclosure of which are herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a low-profile electricalinterconnector with contact members fusion bonded to a substrate thatforms a seal around the contact member to reduce solder wicking. Thesubstrate is bonded to an insulator housing so distal portions of thecontact members are located in through holes.

BACKGROUND OF THE INVENTION

Traditional IC sockets are generally constructed of an injection moldedplastic, insulator housing that includes stamped and formed copper alloycontact members stitched or inserted into recesses. The assembled ICsocket is then generally processed through a reflow oven to attachsolder balls to the contact members.

During final assembly the contact pads on the printed circuit board(“PCB”) are printed with solder paste or flux and the solder balls onthe IC socket are placed in registration with the contact pads. Theassembly is then reflowed and the solder balls essentially weld the ICsocket to the PCB,

During use, an IC socket receives an IC device, such as a packagedintegrated circuit. The contact members electrically couple theterminals on the IC device with the corresponding terminal on the PCB.The terminals on the IC device are typically held against the contactmembers by applying a load, which is expected to maintain intimatecontact and reliable circuit connection throughout the life of thesystem without a permanent connection. As a result, the IC device can beremoved or replaced without the need for reflowing solder connections.

These types of IC sockets and interconnects have been, produced in highvolume for many years. As IC devices advance to next generationarchitectures traditional. IC sockets, have reached mechanical andelectrical limitations that require alternate methods.

As processors and systems have evolved, several factors have impactedthe design of traditional IC sockets. Increased terminal counts,reductions in the distance between the contacts known as terminal pitch,and signal integrity have been main drivers that impact the socket andcontact design. As terminal counts go up, the IC package essentiallygets larger due to the additional space needed for the terminals. As thepackage grows larger, costs go up and the relative flatness of the,package and corresponding PCB require compliance between the contact andthe terminal pad to accommodate the, topography differences and maintainreliable, connection.

Package producers tend to drive the terminal pitch smaller so they canreduce the size of the package as well as the flatness effects. As theterminal pitch reduces, the available area to place a contact is alsoreduced, which limits the space available to locate a spring or contactmember which can deflect without touching a neighbor. In order tomaximize the length of the spring so that it can deflect the properamount without damage, the thickness of the insulating walls within theplastic housing is reduced which increases the difficulty of molding aswell as the latent stress in the molded housing, resulting in warpageduring the heat applied during solder reflow. For mechanical reasons,the contact designs desire to have a long contact that has the properspring properties. Long contact members tend to reduce the electricalperformance of the connection by creating a parasitic effect thatimpacts the signal as, it travels through the contact. Other effectssuch as contact resistance impact the self-heating effects as currentpasses through power delivering contacts, and the small space betweencontacts can cause distortion as a nearby contact influences theneighbor which is known as cross talk. Traditional socket methods areable to meet the mechanical compliance requirements of today's needs,but they have reached an electrical performance limit.

Traditional sockets are manufactured from bulk plastic material that ismachined to, provide device location features as well as positions forthe electrical contacts that can be stamped and formed, blanked, wireelectro-discharge machining processed, or constructed from conductiveelastomer, coil spring probes, or several variations. The predominantcontact type used in sockets is the spring probe, which basicallyconsists of two or more metal members that engage each other to createthe electrical path biased by a coil spring that provides normal andreturn force.

Traditional electrical contacts are press fit into the insulatorhousing. A polymer in the insulator housing is displaced duringinsertion to create an interference fit which holds the electricalcontact in position. In some cases a flowable elastomeric material isdispensed onto the surface of the insulator, which flows into theinsulator housing near the electrical contacts. When cured the flowablematerial holds the electrical contact in position.

Next generation systems will operate above 5 GHz and beyond and theexisting interconnects will not achieve acceptable performance levelswithout significant revision. A major issue with the use of springprobes in sockets is the electrical performance is degraded by the coilspring which is an inductor, as well as the potential capacitance of themetal members and the relatively high contact resistance due to thevarious sliding connection point.

BRIEF SUMMARY OF THE INVENTION

The present disclosure is directed to a method of making an electricalinterconnector. A plurality of contact members are positioned in throughholes in a substrate so distal portions of the contact members extendabove a first surface of the substrate in a cantilevered configurationand proximal portions of the contact members are accessible along asecond surface of the substrate. A flowable polymeric is located on thesecond surface of the substrate adjacent the through holes. Thesubstrate and the contact members are subject to sufficient energyand/or pressure so the flowable polymeric layer flows into engagementwith the proximal portions of the contact members and fuses the contactmembers to the substrate. Distal portions of the contact members arepositioned in through holes in an insulator housing. The first surfaceof the substrate is bonded to a first surface of the insulator housingso the distal portions are accessible from a second surface of theinsulator housing.

The flowable polymeric material is fused to the contact members andsubstantially seals the through holes in the substrate. In oneembodiment, distal portions of the contact members are formed with aplurality of beams maintained in a cantilevered relationship withrespect to the first surface of the substrate. The beams elasticallydeform or flex to mechanically and electrically engage with terminals oncircuit members.

The flowable polymeric material can be a layer positioned on the secondsurface of the substrate. The flowable polymeric material is thenprocessed to reveal the proximal portions of the contact members, suchas by imaging, or laser drilling. Alternatively, the flowable polymericmaterial is molded or deposited on the second surface of the substrateadjacent the through holes. The flowable polymeric material can be a lowmelt liquid crystal polymer, an epoxy set resin, a thermoset material,or a thermoplastic material.

In one embodiment, the substrate is formed from a first polymericmaterial have a first glass transition temperature and the flowablepolymeric material from a second polymeric material have a second glasstransition temperature. The second glass transition temperature is lowerthan the first glass transition temperature. The substrate and thecontact members are, subjected to sufficient energy and/or pressure sothe second glass transition temperature of the flowable polymericmaterial is exceeded, but the first glass transition temperature is notexceeded, so that the flowable polymeric material enters a molten orrubber-like state and flows into engagement with proximal portions ofthe contact members.

In one embodiment, the, method includes electrically coupling proximalportions of the contact members to contact pads on a first circuitmember. Terminals on a second circuit member are positioned in thethrough holes along the second surface of the insulator housing, andmechanically and electrically coupled to the distal portions of thecontact members.

In another embodiment, solder ball terminals on a BGA device arepositioned in the through holes along the second surface of theinsulator housing. The distal portions of the contact members areelastically deformed or flex to mechanically and electrically engagewith the solder ball terminals on the BGA device.

The present disclosure is also directed to an electrical interconnector.A plurality of contact members are located in through holes in asubstrate so distal portions of the contact members extend above a firstsurface of the substrate in a cantilevered configuration and proximalportions of the contact members are accessible along a second surface ofthe substrate. A flowable polymeric material located on the secondsurface of the substrate is fusion bonded to the proximal portions ofthe contact members so the flowable polymeric material substantiallyseals the through holes in the substrate. An insulator housing is bondedto the first surface of the substrate with the distal portions of thecontact members located in through holes in an insulator housing, so thedistal portions are accessible from a second surface of the insulatorhousing.

In one embodiment, the distal portions of the contact members include aplurality of beams maintained in a cantilevered relationship withrespect to the first surface of the substrate. The beams elasticallydeform or flex to mechanically and electrically engage with terminals ona circuit member.

In one embodiment, the substrate is formed from a first polymericmaterial have a first glass transition temperature and the flowablepolymeric material from a second polymeric material have a second glasstransition temperature, wherein the second, glass transition temperatureis lower than the first glass transition temperature.

The present disclosure is also directed to an electrical assemblyincluding contact pads on a first circuit member electrically coupledproximal portions of the contact members. Terminals on a second circuitmember are positioned in the through holes along the second surface ofthe insulator housing, and mechanically and electrically coupled withdistal portions of the contact members.

In an alternate embodiment, the electrical assembly includes solder ballterminals on a BGA device positioned in the through holes along thesecond surface of the insulator housing. The distal portions of thecontact members are mechanically and electrically coupled with thesolder ball terminals on the BGA device.

The contact members can be stamped, formed, etched or fabricated fromconventional means and assembled loose or retained on a strip until theyare removed and installed. The contact members can be of virtually anysize and shape. The insulator housing can be constructed with a varietyof techniques, such as injection molding, laminated in layers usingtraditional circuit board fabrication techniques, printed by depositingpolymers in desired locations, or a combination thereof.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A and 1B are cross sectional views of a multi-layered insulatorhousing for an electrical connector with a flowable contact retentionregion in accordance with an embodiment of the present disclosure.

FIGS. 2A and 2B are cross sectional views of an alternate multi-layeredinsulator housing for an electrical connector with a flowable contactretention region in accordance with an embodiment of the presentdisclosure.

FIG. 3 is a cross sectional view of a molded insulator housing for anelectrical connector with a flowable; contact retention region inaccordance with an embodiment of the present disclosure.

FIG. 4 is a cross sectional view of an insulator housing for anelectrical connector with a printed flowable contact retention region inaccordance with an embodiment of the present disclosure.

FIGS. 5A and 5B are cross sectional views of a multi-layered insulatorhousing for an electrical connector with a plurality of flowable contactretention regions in accordance with an embodiment of the presentdisclosure.

FIG. 6A-6B are cross sectional views of spring contact members in anelectrical connector with a plurality of flowable contact retentionregions in accordance with an embodiment of the present disclosure.

FIGS. 7A and 7B are exploded views of a socket with a flowable contactretention region in accordance with an embodiment of the presentdisclosure.

FIG. 7C is a side sectional view of the socket of FIG. 7A.

FIG. 7D is a perspective view of an array of contacts for use in thesocket of FIG. 7A.

FIGS. 7E-7G illustrate alternate contacts suitable for use in the socketof FIG. 7A.

FIG. 7H is a side view of an electrical interconnect with electroplatedterminals coupled to a BGA device engaged with the socket of FIG. 7A inaccordance with an embodiment of the present disclosure.

FIG. 8 is a cross sectional, view of an insulator housing for anelectrical connector with a flowable contact retention region inaccordance with an embodiment of the present disclosure.

FIG. 9 is a cross sectional view of an insulator housing for anelectrical connector with a printed flowable contact retention region inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B are sectional views of an electrical connector 50 inaccordance with an embodiment of the present disclosure. Insulatorhousing 52 is constructed with a plurality of layers 54A, 54B, 54C, 54D,54E (“54”). In one embodiment, the layers 54 are discrete layers bondedusing a variety of techniques, such as adhesive bonding, ultrasonic orsolvent welding, and other techniques known to those in the art. Inanother embodiment, some of the layers can be molded or machined as asubassembly.

A plurality of through holes 56 are formed in the insulator housing 52to receive contact members 58. The through holes 56 and contact members58 are arranged to correspond with terminals 60 on first circuit member62 and contact pads 64 on second circuit device 66. In the embodimentillustrated in FIG. 1B the terminals 60 are solder balls and the firstcircuit member 62 is an integrated circuit device. The second circuitmember 66 is a PCB.

The layers 54 of the insulator housing 52 can be constructed from avariety of materials, as polyimide or liquid crystal polymer. If theelectrical connector 50 is a rigid structure, one or more of the layers54 can be FR4 or one of many high speed laminates or substrates. If theelectrical connector 50 is a semiconductor package, one of the layers 54can be a material such as FR4, BT resin of any one of a variety oflaminate or substrate materials.

The contact members 58 are preferably sized to loosely fit in thethrough holes 56. The loose-fit arrangement permits vibratory insertionor high speed stitching. The contact members 58 are preferably beamstructures with first end portions 70 locating near first surface 72 ofthe insulator housing 52 and second end portions 74 located near asecond surface 76 of the insulator housing 52.

In the illustrated embodiment, layer of a flowable polymeric material 92is located between layers 54D and 54E in retention region 83. The layerof a flowable polymeric material 92 can be constructed from athermoplastic material, an epoxy set resin, a low-melt liquid crystalpolymer, a thermoset resin, and a variety of other polymeric materials.As best illustrated in FIG. 1B, the flowable material 92 is plasticallydeformed by applying energy and/or pressure to the electrical connector50. The energy can be, for example, heat, ultrasonic stimulation,infrared RF, or some combination thereof. Pressure 61 is also preferablyapplied to facilitate the flow of the flowable polymeric material 92into engagement with the contact members 58. By controlling the quantityand, duration of energy applied to the electrical connector 50 it ispossible to form seal 93 around the contact member 58 in the engagementregion 83, without compromising the structural integrity of theinsulator housing 52. The seal 93 serves to both retain the contactmember 58 in the insulator housing 52 and reduce solder 80 from wickinginto the through holes 56.

In the illustrate embodiment, the flowable material 92 engages withretention features 82 on the contact members 58. The retention features82 reduce the gap between the flowable material 92 and the contactmembers 58 created by the through holes 56.

Locating retention region 83 near the second surface 76 of the insulatorhousing 52 maintains the first end, portions 70 of the contact members58 in a free-floating or cantilevered configuration. Main beams 78 ofthe contact members 58 are configured to flex within the through holes56 when terminals 60 are compressively engaged with the first, endportions 70. Gap 86 is maintained between the layer 54D and the contactmembers 58 in the region 84. Solder balls 80 on second end portions 74of the contact members 58 serve to electrically and mechanically couplethe contact members 58 to the contact pads 64 on the second circuitmember 66.

In one embodiment, the layers 54 are constructed from a first polymericmaterial have a first glass transition temperature and the layer of aflowable polymeric material 92 is preferably constructed from a secondflowable polymeric material with a second glass transition temperaturethat is lower than the first glass transition temperature. After thecontact members 58 are loosely positioning within the through holes 56,the electrical connector 50 is subjected to sufficient energy and/orpressure so the second glass transition temperature of the layer of aflowable polymeric material 92 is exceeded, but the first glasstransition temperature of the first polymeric material is not exceeded.As best illustrated in FIG. 1B, when the layer of a flowable, polymericmaterial 92 is in the glass transition state it flows into engagementwith retention features 82 on the contact members 58 in retention region83 on the insulator housing 52.

The glass-liquid transition or glass transition short is the reversibletransition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle “glassy” stateinto a molten or rubber-like state, as the temperature is increased. Thereverse transition, achieved by cooling the viscous liquid into theglass state, is referred to as vitrification. The glass-transitiontemperature (T_(g)) of a material characterizes the range oftemperatures over which this glass transition occurs. The glasstransition temperature is always lower than the melting temperature(T_(m)) of the crystalline state of the material, if one exists.

Once the electrical connector 50 is cooled so the layer of a flowablepolymeric material 92 is below the second glass transition temperature,the layer of a flowable polymeric material 92 resumes the glass state(i.e., vitrification) and securely retain the contact members 58 in thethrough holes 56. In one embodiment, the layer of a flowable polymericmaterial 92 preferably substantially surrounds the contact member 58 toprevent wicking of the solder 80 into the insulator housing 52.

After heat-cycling and cooling the flowable polymeric material 92, thecontact members 58 are fused to the retention region 83. As used herein,“fused” or “fusing” refers to bonding or joining a component to apolymeric material by subjecting the polymeric material to sufficientenergy and/or pressure to cause the materials to bond together. In someembodiments, fusing requires the glass transition temperature of thepolymeric material to be temporarily exceeded.

By locating retention region 83 near the second surface 76 of theinsulator housing 52, first end portions 70 of the contact members 58are maintained in a cantilevered relationship with respect to the firstsurface 72. Compressively engaging the first circuit member 62 againstthe electrical connector 50 in direction 94 causes the terminals 60 toflex elastically the first end portions 70 of the contact members 58,primarily along the main beams 78, in direction 96 to form a compressiveelectrical connection between the first end portions 70 and theterminals 60.

In one embodiment, the flowable polymeric material 92 is a lowtemperature LCP. LCP's are a class of aromatic polyester polymers thatare extremely unreactive and inert so as to be useful for electricalapplications. Liquid crystal polymers are a rod-like molecularstructure, rigidness of the long axis, and strong dipoles and/or easilypolarizable substituents. The distinguishing characteristic of theliquid crystalline state is the tendency of the molecules to point alonga common axis. This is in contrast to molecules in the liquid phase,which have no intrinsic order. In the solid state, LCP molecules arehighly ordered and, have little translational freedom.

liquid-crystal polymers are available in melted/liquid or solid form.The melting temperatures ranges from about 280° C. to about 400° C. andglass transition temperatures range from about 145° C. to about 400° C.,providing sufficient range to select appropriate materials for the firstand second polymeric materials.

In solid form the main example of lyotropic LCPs is the commercialaramid known as Kevlar. In a similar way, several series of thermotropicLCPs have been commercially produced by several companies (e.g.,Vectran/Ticona). LCP materials have a dielectric constant of about 2.9at a frequency of about 20 GHz, a co-efficient of thermal expansion ofabout 8 to about 17 ppm/degree C., and a dimensional, stability of lessthan about 0.1%. Use of LCP material in circuit structures is disclosedin U.S. Pat. Publ. No. 2016/0014908 (Rathburn), which is herebyincorporated by reference.

Another advantage to the multilayer insulator housing 52 is that bymodifying the dielectric properties of the layers 54 in a region aroundthe contact members 58 at specific points relative to the contactgeometries, changes in the capacitive field can be made to offset the,inductance of the contact members 58. This “impedance tuning” can bedone using a variety of techniques, including adding a continuous layerof a higher dielectric constant material, by varying the dielectricconstants of the housing layers 54, or by adding localized metal atmultiple points within a layer or region adjacent to the contact members58. In the context of the present multi-layered socket housing, thesechanges may include increasing the thickness of the center layers 54Crelative to the surface layers 54A, 54E, selecting a material for thecenter layer 54C with a higher dielectric constant, maintain an air gapbetween the center layer 54C and the contact members 58, and/or addingmetal to portions of the socket housing to surround the contact members58, each of which is discussed in U.S. patent application Ser. No.14/565,724, entitled Performance Enhance Semiconductor Socket, filedDec. 10, 2014, which is hereby incorporated by reference. The variousstructures for impedance tuning may be used alone or in combination witheach other. The various structures for impedance tuning may be usedalone or in combination with each other.

FIGS. 2A and 2B are sectional views of an alternate electrical connector100 in accordance with an embodiment of the present disclosure.Insulator housing 102 is constructed with a plurality of layers 104A,104B, 104C, 104D, 104E, 104F (“104”). A plurality of through holes 106are formed in the insulator housing 102 to receive contact members 108.The through holes 106 and contact members 108 arc arranged to correspondwith terminals 110 on first circuit member 112 and contact pads 114 onsecond circuit device 116.

The contact members 108 are preferably sized to loosely fit in thethrough holes 106. The contact members 108 are preferably dual-beamstructures with first end portions 114 located near first surface 116 ofthe insulator housing 102 and second end portions 118 located near asecond surface 120 of the insulator housing 102. Main beams 122 of thecontact members 108 are configured to flex outward in direction 120within the through holes 106 when terminals 110 are compressivelyengaged with the first end portions 114.

In one embodiment, the layers 104A, 104B, 104C, 104D, and 104F arcpreferably constructed from a first polymeric material have a firstglass transition temperature. The layer 104E is preferably constructedfrom a flowable polymeric material with a second glass transitiontemperature that is lower than the first glass transition temperature.After the contact members 108 are loosely positioning within the throughholes 106, the electrical connector 100 is subjected to sufficientenergy and/or pressure so the second glass transition temperature of thesecond flowable polymeric material is exceeded, but the first glasstransition temperature of the first polymeric material is preferably notexceeded.

As best illustrated in FIG. 2B, the second flowable polymeric material(i.e., layer 104E) enters a molten or rubber-like state and flows intoengagement with the second end portions 118 of the contact members 108in retention region 124. In the preferred embodiment, the secondflowable polymeric material seals the contact members 108 to theinsulator housing 102 to reduce solder wicking.

In an alternate embodiment, pressure 126 is used to plastically deformthe layer 104E to achieve the configuration illustrated in FIG. 2B. Oncethe layer of flowable polymeric, material 104E is in physical contactwith the contact members 108 in the retention region 124, heat isapplied to cure the layer 104E, thereby forming seal 128 with thecontact members 108.

FIG. 3 is a sectional view of an alternate electrical connector 150where the insulator housing 152 is molded to include first and secondpolymeric materials 154, 156 in accordance with an embodiment of thepresent disclosure. In one embodiment, the insulator housing 152 isco-injection molded by sequentially injecting the first and secondpolymeric materials 154, 156. The polymeric materials 154, 156 intersectat interface region 160, but preferably to not substantially mix.

A plurality of through holes 162 are formed in the insulator housing 152to receive contact members 164. The contact members 164 include aretention feature 170 that engages primarily with the second flowablepolymeric material 156 in the insulator housing 152 at retention region174. The through holes 162 are sized to maintain gaps 166 in the regionof the insulator housing 152 constructed from the first polymericmaterial 154 to permit flexure in flexure region 172 during engagementwith circuit member 168. The gap 166 facilitates insertion of thecontact members 164 before reflow and prevents engagement with thecontact member 164 in the flexure region 172 during reflow of the secondflowable polymeric material 156. As discussed herein, energy and/orpressure is applied to the electrical connector 150 so the secondflowable polymeric material 156 flows and is fused to the contact member164 in the retention region 174.

FIG. 4 is a sectional view of an alternate electrical connector 200where the insulator housing 202 is molded from a first polymericmaterial 204 and the second flowable polymeric material 206 isselectively printed in retention region 208 in accordance with anembodiment of the present disclosure. In the illustrated embodiment, thefirst polymeric material 204 is molded with recesses 220 configured toreceive the second flowable polymeric material 206. The second flowablepolymeric material 206 is preferably printed on the insulator housing202 before insertion of contact members 210.

Energy and/or pressure is applied to the electrical connector 200 so thesecond flowable polymeric material 206 flow and fuses with the contactmember 210 in the retention region 208. In the illustrated embodiment,the second flowable polymeric material 206 engages with retentionfeature 212 on the contact members 210. In one embodiment, the secondflowable polymeric material 206 substantially surrounds the perimeter ofthe contact member 210 in the retention region 208 to reduce wicking ofsolder 222 into the insulator housing 202.

FIGS. 5A and 5B are sectional views of an electrical connector 250 inaccordance with an embodiment of the present disclosure. Insulatorhousing 252 is constricted with a plurality of layers 254A, 254B, 254C,254D, 254E, 250F, 250G (“254”). In the illustrated embodiment, layers ofa flowable polymeric material 256 are located between the layers 254D,254E, 254F, 254G. The layers 254, 256 are preferably bonded using avariety of techniques, such as adhesive bonding, ultrasonic or solventwelding, and other techniques known to those in the art. In anotherembodiment, some of the layers can be molded or machined as asubassembly after the fact.

Through holes 258 extend from first surface 260 to second surface 262.In the illustrate embodiment, through holes 258 in the layers 254E,254F, 2540 are sized to create contours 264 that generally correspondswith shape of retention features 266 of contact members 268. Thecomplementary shapes of the contour 264 and the retention features 266brings the flowable layers 256 in close proximity to bridge the gapthere between.

The contact members 268 are preferably sized to loosely fit in thethrough holes 258. The contact members 268 have a shape and functiongenerally as discussed in connection with FIGS. 1A and 1B.

As best illustrated in FIG. 5B, the flowable material 256 is plasticallydeformed by applying energy and/or pressure 253 to the electricalconnector 250. By controlling the quantity and duration of energy and/orpressure 253 applied to the electrical connector 250 it is possible toform seal 270 around the contact member 268 in engagement region 272,without compromising the structural integrity of the insulator housing252. The seal 270 serves to both retain the contact member 268 in theinsulator housing 252 and inhibits solder 274 from wicking into thethrough holes 258.

FIGS. 6A and 6B are sectional views of alternate electrical connector300 with insulator housing 302 retaining, spring contact members 304.The insulator housing 302 is constructed from multiple layers 306A,306B, 306C, 306D, 306E, 306F (“306”) in accordance with an, embodimentof the present disclosure. In one embodiment, layers of a flowablepolymeric material 308 are located between the layers 306C, 306D, 306E,306F. Additional details about insulator housings with spring contactmembers applicable to this disclosure are disclosed in U.S. Pat. No.8,758,067 (Rathburn) and U.S. Pat. Publ. 2015/0091600 (Rathburn), filedDec. 10, 2014, the disclosures of which are hereby incorporated byreference in their entireties.

The spring contact members 304 are of a conventional structure with anupper portion 310 that slides axially relative to lower portion 312.Spring member 314 located in through holes 330 biases the upper portion310 away from the lower portion 312 along axis 316. In application,upper portion 310 extends above top surface 320 of the insulator housing302 to engage with contact members on the IC device 322. Simultaneously,lower portion 312 extends beyond lower surface 324 of the insulatorhousing 302 to engage with contact pads 326 on the PCB 328. The lowerportion 312 is typically soldered to the contact pads 326.

The through holes 330 in the layers 306D, 306E, 306F are sized to followcontour of the lower portion 312. Applying energy and/or pressure to theelectrical contact 300 causes plastic deformation of the layers of aflowable polymeric material 308, which forms a seal 332 around the lowerportion 312 at retention region 334 to prevent solder wicking.

FIGS. 7A through 7C illustrate a surface mount technology BGA socket 350with a layer of a flowable polymeric material 352 in accordance with anembodiment of the present disclosure. Contact members 354 are insertedin preformed openings 356 in substrate 358. After insertion, the layerof flowable polymeric material 352 is positioned over proximal ends 360of the contact members 354. Energy and/or pressure is applied to flowthe layer of flowable polymeric material 352 into engagement with thecontact members 354. The contact members 354 are now mechanicallyretained to the substrate 358. The flowable polymeric material 352 alsoforms a seal around the contact members 354 in the openings 356, so thatwhen solder balls 364 are attached and subsequent reflowed to circuitboard 376 the solder 364 is prevented from wicking up the contactmembers 354 and into the insulator housing 370. In an alternateembodiment, the flowable polymeric material 352 is molded or depositedon the substrate 358 adjacent the openings 356.

The substrate 358 containing the contact members 354 can be inverted toexpose proximal ends 360 of the contact members 354, which willtypically connect to the printed circuit board during final assembly.The rear surface of the substrate 358 and the exposed proximal ends 360of the contact members 354 can be treated as a field of connectionpoints for further enhancement that provides contact retention, addscircuit features not normally embedded within a socket, adds mechanicalfeatures to improve the reliability of the solder joint to the PCB, andprovides a platform to add passive and active circuit features toimprove electrical performance or internal function and intelligence,such as disclosed in commonly assigned U.S. Pat. No. 8,955,215(Rathburn), which is hereby incorporated by reference.

In the illustrated embodiment, the flowable polymeric material 352preferably includes an array of openings 362 that correspond with theproximal ends 360 of the contact members 354 so that solder balls 364can be applied. In an alternate embodiment, the flowable polymericmaterial 352 is applied as a continuous sheet without the openings 362and the openings 362 arc subsequently drilled, such as with a laser.Distal ends 366 of the contact members 354 are then positioned inopenings 368 in insulator housing 370.

For some applications Cu may be too soft to be used as the contactmembers 354, so CuNiSi or other copper alloy may be substituted. In the,illustrate embodiment, the contact members 354 do not include contactretention features, greatly reducing the complexity of the component andthe tooling required to produce them. After insertion, the flowablepolymeric material 352 retains the contact members 354 in the socket350.

As best illustrated in FIG. 7C, the socket 350 enables direct socketingof BGA device 372 without reflow to the solder balls 374. The socket 350permits the BGA device 372 to be removable and replaceable without theneed for rework or reflow of the solder balls 374. The socket 350 itselfis soldered to PCB 376. The distal portions 366 of the contact members354 are shaped to accept the solder balls 374 on the BGA device 372 in amanner that retains the BGA device 372, but allows the BGA device 372 tobe lifted out.

The challenge with this type of product is to create an interfacebetween the solder ball 374 on the BGA device 372 and the contact tips366 such that the BGA device 372 can be inserted with low enough forceto enable insertion by hand, while still providing stable contactresistance and reliable connection. Related to this challenge is theextraction force relative to insertion force such that the BGA device372 can be easily removed by hand or with the aid of a tool withoutbreaking solder joints 380 between the contact members 354 and the PCB376 as well as the joint, from the BGA device 372 to the solder balls374.

As best illustrated in FIG. 7B, distal portions 366 of the contactmembers 354 include contact tips 382 that score the solder balls 374during insertion to remove oxides. Adjacent a curved region 384 has adiameter corresponding to a diameter of the solder balls 374 to capturethe solder balls 374 in the insulator housing 370. Once the BGA device372 is fully seated there will be a slight engagement of the contacttips 382 beyond the upper hemisphere 386 of the solder ball 374 diameterto retain the solder ball 374 in the insulator housing 370. Severalvarieties of contact shapes and geometries can be formed to optimize theinterface and reliability, with multiple points of contact greatlyenhancing probability of reliable connection as well as reducinginductance and contact resistance. (See FIGS. 7E-7G).

The intent of the design is to “loosely” or slightly cradle the solderballs 374 on the BGA device 372 in the openings 368 in the insulatorhousing 370. The openings 368 in the insulator housing 370 are sized topermit the beams 388 to flex slightly while the openings 368 in theinsulator housing 370 prevent over deflection of the beams 388. Thebeams 388 can also be shorter to minimize the height of the socket 350.The contact members 354 can also be coined or formed with a single beam388 that closely surrounds the solder balls 374 to provide multiplepoints of contact as well as reduce metal content to improve capacitiveeffects.

FIG. 7D illustrates an array 390 of contact members 354 stamped andformed on grid that matches the pattern of the openings 356 in thesubstrate 358. The contact members 354 are simultaneously engaged withthe substrate 358. The portions 392 of the array 390 that hold thecontact members 354 together are then removed by etching, laser cutting,or the like.

FIGS. 7E-7G illustrate alternate configurations of the contact members354 in accordance with an embodiment of the present disclosure. FIGS. 7Eand 7F illustrate embodiments with three beams 388. All of the beams 388can flex radially outward. FIG. 7G is illustrates a folded structurewith paired beams 394A, 394B, where the respective pairs 394 flex, awayfrom each other along axis 396.

FIG. 7H is a side view of an electrical interconnect 500 withelectroplated terminals 502 coupled to a BGA device 504 engaged with thesocket 350 of FIG. 7A in accordance with an embodiment of the presentdisclosure. Details of the electrical interconnect 500 are disclosed incommonly owned U.S. patent Ser. No. 14/408,039, filed Mar. 13, 2013,entitled HIGH SPEED CIRCUIT ASSEMBLY WITH INTEGRAL TERMINAL AND MATINGBIAS LOADING ELECTRICAL CONNECTOR ASSEMBLY, the disclosure of which ishereby incorporated by reference.

FIG. 8 is a side cross-sectional view of a portion of a semiconductorsocket 400 in accordance with an embodiment of the present disclosure.Substrate 402 includes an array of through holes 404 that extend from afirst surface 406 to a second surface 408. Recesses 410 are formed inthe second surface 408 that overlaps with the through holes 404. Thesubstrate 402 can be configured to engage with a variety of circuitmembers 412, such as example, IC device 412. As used herein, the term“circuit member” refers to, for example, a packaged integrated circuitdevice, an unpackaged integrated circuit device, a printed circuitboard, a flexible circuit, a bare-die device, an organic or inorganic,substrate, a rigid circuit, or any other device capable of carryingelectrical current.

A plurality of discrete contact members 414 are inserted into recesses410 so distal portions 416 extend out through the holes 404. In theillustrated embodiment, the distal portions 416 are simple cantileverbeams located above the first surface 406. The distal portions 416preferably have a generally uniform cross section. Proximal portions 418of the contact members 414 are preferably configured to reside in therecesses 410. The contact members 416 can be positioned into therecesses 410 using a variety of techniques, such as for examplestitching or vibratory techniques. The contact members 414 arepreferably constructed of copper or similar metallic materials such asphosphor bronze or beryllium-copper. The contact members are preferablyplated with a corrosion resistant metallic material, such as nickel,gold, silver, palladium, or multiple layers thereof. Semiconductorsockets such as illustrated in FIGS. 8 and 9 are disclosed incommonly-assigned U.S. patent application Ser. No. 13/319,158 entitledSemiconductor Socket, filed Jun. 15, 2010, and Ser. No. 14/408,338entitled Semiconductor Socket with Direct Metalization, filed Mar. 14,2013, the entire disclosures of which are hereby incorporated byreference.

In one embodiment, the entire substrate 402 is substantially constructedfrom a low glass transition temperature polymeric material. Duringreflow the polymeric material of the substrate 402 engages with theproximal portions 418. After cooling, the substrate 402 is bonded andsealed to the proximal portions 418 in the retention region 420,preventing solder 422 from wicking into the recesses 410.

In an alternate embodiment, the substrate 402 is constructed from a highglass transition temperature polymeric material and the inside surfaceof the recesses 410 are printed with lower glass transition polymericmaterial 422. During reflow the polymeric material 422 engages with theproximal portions 418.

FIG. 9 is a cross-sectional view of an interconnect assembly 450 in,accordance with an embodiment of the present disclosure. Substrate 452includes an array of through holes 454 that extend from a first surface456 to a second surface 458. Recesses 458 are formed in the secondsurface 456 that overlaps with the through holes 454.

Substrate 452 is constructed from a high glass transition temperaturepolymeric material. Recess 458 in the substrate 452 is filed with lowglass temperature polymeric material 460. The polymeric material 460 canbe molded with the substrate 452 or be deposited in the recess 458 afterthe substrate 452 is formed. The through holes 454 also extend throughthe polymeric material 460.

A plurality of discrete contact members 462 are inserted into thethrough holes 454. In the illustrated embodiment, the contact members462 are simple cantilever beams without any retention features. Duringreflow the polymeric material 460 engages with proximal portions 464 ofthe contact members 462. After cooling, the substrate 452 is bonded andsealed to the proximal portions 464 in retention region 466. Solderballs 468 are printed onto the proximal end 470 of the contact member462. The polymeric material 460 forms a seal in the retention region 466to prevent solder 468 from wicking into the through holes 454.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the embodiments of the, disclosure.The upper and lower limits of these smaller ranges which mayindependently be included in the smaller ranges is also encompassedwithin the embodiments of the disclosure, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either both of those includedlimits are also included in the embodiments of the present disclosure.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the embodiments of the present disclosure belong.Although any methods and materials similar or equivalent to thosedescribed herein can also be used in the practice or testing of theembodiments of the present disclosure, the preferred methods andmaterials are now described. All patents and publications mentionedherein, including those cited in the Background of the application, arehereby incorporated by reference to disclose and described the methodsand/or materials in connection with which the publications are cited.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present disclosure isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need, to be independently confirmed.

Other embodiments of the disclosure are possible. Although thedescription above contains much specificity, these should not beconstrued as limiting the scope of the disclosure, but as merelyproviding illustrations of some of the presently preferred embodimentsof this disclosure. It is also contemplated that various combinations orsub-combinations of the specific features and aspects of the,embodiments may be made and still fall within the scope of the presentdisclosure. It should be understood that various features and aspects ofthe disclosed embodiments can be combined with or substituted for oneanother in order to form varying modes of the disclosed embodiments ofthe disclosure. Thus, it is intended that the scope of the presentdisclosure herein disclosed should not be limited by the particulardisclosed embodiments described above.

Thus the scope of this disclosure should be determined by the appendedclaims and their legal equivalents. Therefore, it will be appreciatedthat the scope of the present disclosure fully encompasses otherembodiments which may become obvious to those skilled in the art, andthat the scope of the present disclosure is accordingly to be limited bynothing other than the appended claims, in which reference to an elementin the singular is not intended to mean “one and only one” unlessexplicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiments) that are known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the present claims. Moreover, itis not necessary for a device or method to address each and everyproblem sought to be solved by the present disclosure, for it to beencompassed by the present claims. Furthermore, no element, component,or method step in the present disclosure is intended to be dedicated tothe public regardless of whether the element, component, or method stepis explicitly recited in the claims.

What is claimed is:
 1. A method of making an electrical interconnector,the method comprising the steps of: positioning a plurality of contactmembers in through holes in a substrate, so distal portions of thecontact members extend above a first surface of the substrate in acantilevered configuration and proximal portions of the contact membersare accessible along a second surface of the substrate; locating aflowable polymeric on the second surface of the substrate adjacent thethrough holes; subjecting the substrate and the contact members tosufficient energy and/or pressure so the flowable polymeric layer flowsinto engagement with the proximal portions of the contact members andfuses the contact members to the substrate; positioning distal portionsof the contact members in through holes in an insulator housing; andbonding the first surface of the substrate to a first surface of theinsulator housing so the distal portions are accessible, from a secondsurface of the insulator housing,
 2. The method of claim 1 wherein theflowable polymeric material fused to the contact members substantiallyseals the through holes in the substrate.
 3. The method of claim 1comprising forming distal portions of the contact members with aplurality of beams maintained in a cantilevered relationship withrespect to the first surface of the substrate.
 4. The method of claim 1comprising forming distal portions of the contact members with aplurality of beams that elastically deform to mechanically andelectrically engage, with terminals on circuit members.
 5. The method ofclaim 1 comprising positioning a layer of the flowable polymericmaterial on the second surface of the substrate.
 6. The method of claim5 comprising processing the flowable polymeric material to reveal theproximal portions of the contact members.
 7. The method of claim 1comprising molding the flowable polymeric material to the second surfaceof the substrate adjacent the through holes.
 8. The method of claim 1comprising depositing the flowable polymeric material on the secondsurface of the substrate adjacent the through holes.
 9. The method ofclaim 1 selecting the flowable polymeric material from low melt liquidcrystal polymer, an epoxy set resin, a thermoset material, or athermoplastic material.
 10. The method of claim 1 comprising: forming,the substrate from a first polymeric material have a first glasstransition temperature and the flowable polymeric material from a secondpolymeric material have a second glass transition temperature, whereinthe second glass transition temperature is lower than the first glasstransition temperature; and subjecting the substrate and the contactmembers to sufficient energy and/or pressure so the second glasstransition temperature of the flowable polymeric material is exceeded,but the first glass transition temperature is not exceeded, so that theflowable polymeric material enters a molten or rubber-like state andflows into engagement with proximal portions of the contact members. 11.The method of claim 1 comprising: electrically coupling proximalportions of the contact members to contact pads on a first circuitmember; positioning terminals on a second circuit member in the throughholes along the second surface of the insulator housing; andmechanically and electrically coupling the terminals on the secondcircuit member with distal portions of the contact members.
 12. Themethod of claim 1 comprising: positioning solder ball terminals on a BGAdevice in the through holes along the second surface of the insulatorhousing; and elastically deforming distal portions of the contactmembers to mechanically and electrically engage with the solder ballterminals on the BGA device.
 13. An electrical interconnectorcomprising: a plurality of contact members located in through holes in asubstrate so distal portions of the contact members extend above a firstsurface of the substrate in a cantilevered configuration and proximalportions of the contact members are accessible along a second surface ofthe substrate; a flowable polymeric material located on the secondsurface of the substrate is fusion bonded to the proximal portions ofthe contact members so the flowable polymeric material substantiallyseals the through holes in the substrate; and an insulator housingbonded to the first surface of the substrate with the distal portions ofthe contact members located in through holes in an insulator housing, sothe distal portions are accessible from a second surface of theinsulator housing.
 14. The electrical interconnect of claim 13 whereindistal portions of the contact members comprise a plurality of beamsmaintained in a cantilevered relationship with respect to the firstsurface of the substrate.
 15. The electrical interconnect of claim 13wherein distal portions of the contact members comprise a plurality ofbeams that elastically deform to mechanically and electrically engagewith terminals on a circuit member.
 16. The electrical interconnect ofclaim 13 wherein the flowable polymeric material is selected from one ofa low melt liquid crystal polymer, an epoxy set resin, a thermosetmaterial, or a thermoplastic material.
 17. The electrical interconnectof claim 13 wherein the substrate is formed from a first polymericmaterial have a first glass transition temperature and the flowablepolymeric material from a second polymeric material have a second glasstransition temperature, wherein the second glass transition temperatureis lower than the first glass transition temperature
 18. An electricalassembly comprising: the electrical interconnect of claim 13; contactpads on a first circuit member electrically coupled proximal portions ofthe contact members; terminals on a second circuit member positioned inthe through holes along the second surface of the insulator housing, andmechanically and electrically coupled with distal portions of thecontact members.
 19. An electrical assembly comprising: the electricalinterconnect of claim 13; solder ball terminals on a BGA devicepositioned in the through;holes along the second surface of theinsulator housing, the distal portions of the contact membersmechanically and electrically coupled with the solder ball terminals onthe BGA device.